Faculty of computer engineering information security direction

Quality and reliability

Main articles: Software quality and Software testing
Software quality is very important, especially for commercial and system software. If software is faulty, it can delete a person's work, crash the computer and do other unexpected things. Faults and errors are called "bugs" which are often discovered during alpha and beta testing.^{[citation needed]} Software is often also a victim to what is known as software aging, the progressive performance degradation resulting from a combination of unseen bugs.^{[citation needed]}
Many bugs are discovered and fixed through software testing. However, software testing rarely—if ever—eliminates every bug; some programmers say that "every program has at least one more bug" (Lubarsky's Law).^[18] In the waterfall method of software development, separate testing teams are typically employed, but in newer approaches, collectively termed agile software development, developers often do all their own testing, and demonstrate the software to users/clients regularly to obtain feedback.^{[citation needed]} Software can be tested through unit testing, regression testing and other methods, which are done manually, or most commonly, automatically, since the amount of code to be tested can be large.^{[citation needed]} Programs containing command software enable hardware engineering and system operations to function much easier together.^[19]

License

Main article: Software license
The software's license gives the user the right to use the software in the licensed environment, and in the case of free software licenses, also grants other rights such as the right to make copies.^[20]
Proprietary software can be divided into two types:

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  freeware, which includes the category of "free trial" software or "freemium" software (in the past, the term shareware was often used for free trial/freemium software). As the name suggests, freeware can be used for free, although in the case of free trials or freemium software, this is sometimes only true for a limited period of time or with limited functionality.^[21]
  
• 
  software available for a fee, which can only be legally used on purchase of a license.^[22]
  

Open-source software comes with a free software license, granting the recipient the rights to modify and redistribute the software.^[23]